Known electrochemical detection methods already make it possible to demonstrate target nucleic acid sequences. Some make use of both nucleic acid amplification processes, for example of PCR (polymerase chain reaction) type, and cyclic voltammetry processes. According to one of these methods, a biological sample containing a nucleic acid, which exhibits a predetermined target nucleotide sequence, is provided and an oxidizing agent capable of oxidizing at least one of the nucleotide bases of the target sequence is added to the biological sample. The amplification means comprise nucleotides of a type including the oxidizable nucleotide base and the nucleotides are of course intended to be consumed during the implementation of the amplification process so as to produce replicated nucleic acid sequences. Simultaneously, or after each amplification step, an electric field is applied to the sample so as to bring about reaction of the oxidizing agent with the oxidizable nucleotide base, and the electric current which consequently passes through the sample is measured. According to this method, described more specifically in document PCT/FR2007/000373, the presence of the predetermined target sequence and the initial amount thereof are determined when the electric current decreases over the course of the amplifications. This is because, during the amplification process, the number of free nucleotides of the amplification means decreases since they are incorporated into the synthesized nucleic acids. The oxidizing agent can then react only with an increasingly limited amount of free nucleotides. Consequently, fewer and fewer electron transfers due to the oxidation reaction occur, and the electric current decreases.
Thus, such a method makes it possible to rapidly detect and quantify the presence of a given nucleic acid in any biological sample.